Danny and Baez team up with Danny's old partner to find a copycat killer emulating a criminal's murders from a previous case; Frank and Mayor Chase battle over how best to handle the city's rising homeless population.
Frank struggles after Joe Hill's lineage as a Reagan is revealed; Erin and Anthony receive gift-wrapped evidence; Danny's opposition to authority clashes with Jamie's adherence to the rules, as both brothers work to solve a murder.
Danny tries to find the source of a deadly narcotic after three teenagers die from an overdose.
Jamie's conduct is questioned when a suspect he was pursuing is fatally injured; Baez goes under cover to investigate a drug dealer -- the fiance of Danny's ex-girlfriend (Charisma Carpenter).
Danny finds a murdered student at a college campus; after reconnecting with a former law-school classmate, Jamie has a life crisis; Erin tries to give Nicky some freedom.
